Double-side display device with surface light source device having deflection patterns

Abstract

A double-side LCD having a surface light source device including a light guide plate and a light source facing one end face of the light guide plate. A plurality of deflection patterns are formed in a surface facing a light outgoing plane of the light guide plate, the deflection pattern includes an inclined plane facing the light source side and a re-incident plane substantially perpendicular to the light outgoing plane. Light from the light source is reflected by the inclined plane and outputted from the light outgoing plane to the LCD. A tilt angle (α) of the inclined plane satisfies: 45°−[Sin −1 (Sin θ/n)]/2≦α≦45°+[Sin −1 (Sin θ/n)]/2, wherein θ is an angle between a direction of peak brightness of outputted light and a direction perpendicular to the light outgoing plane, n is a refractive index of the light guide plate, and θ is within 6-15°.

1. A double-side display device comprising:
 a semi-transmissive liquid crystal panel comprising a liquid crystal layer sealed by sandwiching the liquid crystal layer between two glass substrates, the semi-transmissive liquid crystal panel having a reflecting region and a transmission region; and 
 a surface light source device comprising:
 a light guide plate having a light outgoing plane in a principal plane thereof, the light outgoing plane facing the semi-transmissive liquid crystal panel; and 
 a light source facing one end face of the light guide plate, 
 wherein a plurality of deflection patterns are formed in a surface facing the light outgoing plane of the light guide plate, the deflection pattern including an inclined plane located on a light source side and a re-incident plane substantially perpendicular to the light outgoing plane; 
 light emitted by the light source into the light guide plate is reflected by the inclined plane and then the light is outputted from the light outgoing plane; and 
 a tilt angle (α) of the inclined plane satisfies:
   45°−[Sin −1 (Sin θ/ n )]/2≦α≦45°+[Sin −1 (Sin θ/ n )]/2, 
 
  where θ is an angle formed between a direction of peak brightness of the light outputted from the light outgoing plane and a direction perpendicular to the light outgoing plane, and n is a refractive index of the light guide plate. 
 
 
     
     
       2. The double-side display device according to  claim 1 , wherein the reflecting region and the transmission region are formed in the whole of a display surface in the semi-transmissive liquid crystal panel. 
     
     
       3. The double-side display device according to  claim 1 , wherein the reflecting region and the transmission region are formed piecewise in the semi-transmissive liquid crystal panel. 
     
     
       4. The double-side display device according to  claim 1 , wherein a diffusion layer is formed in an opposite plane to a plane facing the light guide plate in the semi-transmissive liquid crystal panel; and
 a diffusion angle of the diffusion layer is substantially equal to half width at half maximum of view angle characteristics of the light outputted from the light outgoing plane of the light guide plate. 
 
     
     
       5. The double-side display device according to  claim 1 , wherein a reflecting electrode for forming the reflecting region is formed in the semi-transmissive liquid crystal panel; and
 the reflecting electrode has diffusion characteristics, and a diffusion angle of the reflecting electrode is substantially equal to half width at half maximum of view angle characteristics of the light outputted from the light outgoing plane of the light guide plate. 
 
     
     
       6. The double-side display device according to  claim 1 , wherein the semi-transmissive liquid crystal panel includes an antireflective coat or an antireflective structure in a plane facing the light guide plate. 
     
     
       7. The double-side display device according to  claim 1 , wherein the direction of the peak brightness of the light outputted from the light outgoing plane of the light guide plate is inclined toward the opposite side to the light source with respect to a normal perpendicular to the light outgoing plane. 
     
     
       8. The double-side display device according to  claim 1 , wherein the direction of the peak brightness of the light outputted from the light outgoing plane of the light guide plate is inclined toward the light source side with respect to a normal perpendicular to the light outgoing plane. 
     
     
       9. The double-side display device according to  claim 1 , wherein the light guide plate includes an antireflective coat or an antireflective structure in the light outgoing plane. 
     
     
       10. The double-side display device according to  claim 1 , wherein the angle θ is within the range of 6°-15°. 
     
     
       11. The double-side display device according to  claim 1 , wherein a cross section perpendicular to a lengthwise direction of the deflection pattern is formed in a substantially right-angled triangle in the deflection pattern.